1. Field of the invention
The invention relates to a sensor for measuring an oxygen content in a liquid or gaseous sample, comprising                a first sensor section that can be brought into contact with the sample and has a luminescent indicator dye embedded in an oxygen-permeable, first polymer matrix,        light guiding means for guiding luminescence excitation light from a light source to the first sensor section, and        light guiding means for guiding luminescence emission light from the first sensor section to a detector.        
2. Description of the related art
WO 02/103334 A1 discloses an oxygen sensor of the generic type.
It is known about many luminescent dyes, in particular from the group of Pt(II)porphyrins, that their luminescence intensity depends strongly on the oxygen concentration of the medium surrounding the dye. This effect is based on an interaction of the oxygen with the state of the dye molecules energetically excited by excitation light of suitable wavelength. In addition to the luminescence-producing transition from the excited state to the ground state, this interaction can result in an additional radiation free deexcitation path. The probability of this radiation free transition increases with the oxygen concentration. This is called luminescent extinction or quenching by oxygen.
The known sensor utilizes this quenching effect to determine the oxygen content of a sample. Thus, the first sensor section is irradiated with excitation light of suitable wavelength, and the intensity of the luminescence emitted by the indicator dye is measured. Suitable light sources such as, for example, LEDs, and suitable detectors such as, for example, photomultipliers with suitable, upstream filters, are known to the person skilled in the art.
WO 02/103334 A1 addresses as a problem of such a measuring arrangement the dependence of the luminescence intensity not only on the oxygen concentration, but also on fluctuations in the intensity of the excitation light, for example owing to fluctuations in the light source. It is proposed to solve this problem by using a second, oxygen-insensitive dye whose luminescence intensity is determined in the course of a second simultaneous luminescence measurement at the same excitation wavelength and at a separate detection wavelength optimized for the reference dye, and whose ratio with the luminescence intensity value of the indicator dye is formed.
It is disadvantageous with the known sensor that a further, strong dependence, specifically dependence on the temperature of the sensor, that is to say substantially of the sample surrounding the latter, is not taken into account. In addition, the use of a second dye for generating a reference signal entails the disadvantage that said dye can be influenced in a different way from the actual indicator dye by changes in the measuring conditions or by fading.
It is the object of the present invention to make available an oxygen sensor with the aid of which the influences of the temperature on the measuring result can be compensated, and which has no need of a second dye for referencing.